diff --git a/module/spring-boot-web-server/src/main/java/org/springframework/boot/web/server/MimeMappings.java b/module/spring-boot-web-server/src/main/java/org/springframework/boot/web/server/MimeMappings.java
index 1a0c44f8a5f4..0257d500fc44 100644
--- a/module/spring-boot-web-server/src/main/java/org/springframework/boot/web/server/MimeMappings.java
+++ b/module/spring-boot-web-server/src/main/java/org/springframework/boot/web/server/MimeMappings.java
@@ -72,7 +72,8 @@ public MimeMappings(Map<String, String> mappings) {
 	 */
 	MimeMappings(MimeMappings mappings, boolean mutable) {
 		Assert.notNull(mappings, "'mappings' must not be null");
-		this.map = (mutable ? new LinkedHashMap<>(mappings.map) : Collections.unmodifiableMap(mappings.map));
+		Map<String, Mapping> source = mappings.getMap();
+		this.map = (mutable ? new LinkedHashMap<>(source) : Collections.unmodifiableMap(source));
 	}
 
 	/**
@@ -132,7 +133,7 @@ public boolean equals(Object obj) {
 			return true;
 		}
 		if (obj instanceof MimeMappings other) {
-			return getMap().equals(other.map);
+			return getMap().equals(other.getMap());
 		}
 		return false;
 	}
diff --git a/module/spring-boot-web-server/src/test/java/org/springframework/boot/web/server/MimeMappingsTests.java b/module/spring-boot-web-server/src/test/java/org/springframework/boot/web/server/MimeMappingsTests.java
index 7343cc9e563a..28062f1ac683 100644
--- a/module/spring-boot-web-server/src/test/java/org/springframework/boot/web/server/MimeMappingsTests.java
+++ b/module/spring-boot-web-server/src/test/java/org/springframework/boot/web/server/MimeMappingsTests.java
@@ -51,6 +51,28 @@ void createFromExisting() {
 		assertThat(clone.get("baz")).isNull();
 	}
 
+	@Test
+	void createFromDefault() {
+		MimeMappings clone = new MimeMappings(MimeMappings.DEFAULT);
+		assertThat(clone).hasSameSizeAs(MimeMappings.DEFAULT);
+		assertThat(clone.get("html")).isEqualTo("text/html");
+		clone.add("foo", "bar");
+		assertThat(MimeMappings.DEFAULT.get("foo")).isNull();
+	}
+
+	@Test
+	void makeUnmodifiableFromDefault() {
+		MimeMappings unmodifiable = MimeMappings.unmodifiableMappings(MimeMappings.DEFAULT);
+		assertThat(unmodifiable.get("html")).isEqualTo("text/html");
+	}
+
+	@Test
+	void equalsIsSymmetricWithDefault() {
+		MimeMappings clone = new MimeMappings(MimeMappings.DEFAULT);
+		assertThat(clone).isEqualTo(MimeMappings.DEFAULT);
+		assertThat(MimeMappings.DEFAULT).isEqualTo(clone);
+	}
+
 	@Test
 	void createFromMap() {
 		Map<String, String> mappings = new HashMap<>();